Attachment of Therapeutic and Imaging Agents to Magnetotactic Bacteria Acting as Self-Propelled Bio-Carriers for Cancer Treatment

RÉSUMÉ Malgré les progrès de la médecine moderne, les traitements anticancéreux actuels n’arrivent toujours pas à vaincre le cancer. Seulement une fraction des doses de médicaments administrées parvient à la tumeur en raison d’un ciblage non spécifique, de barrières physiologiques au niveau du système vasculaire ainsi que de l’élimination immédiate de médicaments par le système immunitaire. Des dosages fréquents de médicaments deviennent nécessaires afin de surmonter ces obstacles, entraînant une toxicité systémique, des effets secondaires et un échec thérapeutique. De plus, les systèmes actuels d’imagerie médicale sont incapables de produire des images de haute qualité des structures tumorales pour les diagnostiques et les traitements. Ceci est dû aux restrictions de la résolution spatiale et de l’incapacité des agents de contraste à pénétrer dans les zones tumorales afin de générer un signal suffisamment intense. Le développement de nouveaux agents thérapeutiques ainsi que de nouvelles techniques de ciblage thérapeutique sont donc requis afin d’améliorer l’efficacité des traitements actuels. Pour ce projet de recherche doctorale, l'attachement de charges utiles à la surface de bactéries magnétotactiques flagellées Magnetococcus Marinus MC-1 (BMT) a été mise en place pour transporter de façon ciblée une quantité optimale de médicaments profondément dans les zones tumorales. Ces bio-robots autopropulsés de dimensions adéquates sont équipés d’un système de propulsion dirigeable, d’un système de navigation, et de capacités sensorielles. Divers types de complexes BMT ont été fabriquées en attachant aux BMT (i) des liposomes vides (BMT-LP), (ii) des liposomes contenant un agent anticancéreux SN38 (BMT-LSC), et (iii) des nanoparticules superparamagnétiques de magnétite (BMT-S200). L’efficacité de l'attachement des charges et du comportement des bactéries soumises à un champ magnétique directionnel ont été étudiés. Par la suite, la capacité des complexes BMT à naviguer le long d’une trajectoire prédéterminée, à infiltrer profondément l'espace interstitiel, et à cibler des zones tumorales inaccessibles, ont été étudiés dans un modèle animal soumis à un champ magnétique externe. Pour parvenir à des complexes BMT aptes à transporter suffisamment de produits pharmaceutiques et de s’accumuler préférentiellement dans les régions affectées, il faut assurer un attachement solide et stable qui ne compromet pas la motilité des BMT.----------ABSTRACT Despite the substantial achievements of modern medicine, current medical therapies cannot eradicate cancer. Due to nonspecific targeting, the multiple physiological barriers that blood-borne agents must encounter, and the rapid sequestration of drugs by the immune system, a suboptimal fraction of the total injected dose reaches the intended target. These obstacles necessitate frequent dosing to compensate therapeutic effects, resulting in systemic toxicity, undesirable side effects, and treatment failure. In addition, existing medical imaging modalities struggle to provide high quality clinical images of tumor structures for treatment purposes due to limitations in spatial resolution and lack of penetration of contrast agents into tumoral regions to induce sufficient signal intensity. To address these issues, the development of new therapeutic agents alongside improved strategies for targeting therapy with the ability to control their fate is required. The attachment of payloads to the flagellated Magnetococcus Marinus MC-1 magnetotactic bacteria (MTB) to directly transport optimal quantities of pharmaceutical agents to regions located deep in tumors is what has been proposed during the accomplishment of this PhD project. These engineered self-propelled bio-robots with an appropriate dimension are equipped with steerable propulsion, navigation system, and onboard sensory capabilities. MTB complexes were fabricated by attaching the MTB to (i) empty liposomes (MTB-LP), (ii) SN38 anticancer drug encapsulated in liposomes (MTB-LSC), and (iii) 200 nm superparamagnetic magnetite nanoparticles (MTB-S200). The attachment efficacy and magnetic response behavior from the influence of a directional magnetic field of loaded bacteria with therapeutic or imaging agents were studied. Subsequently, results showed that the attachment method was suitable to allow MC-1 MTB to transport therapeutic and imaging agents along a planned trajectory prior to penetrate deep through the interstitial space in order to reach the hypoxic regions of a tumor in an animal model. To achieve MTB complexes capable of carrying sufficient pharmaceutical agents and accumulating preferentially at disease sites, the attachment must be strong and stable without compromising the natural motility of MTB. The MTB-LP were prepared by direct covalent attachment of functionalized liposomes to the amine groups naturally presented on the surface of MTB using carbodiimide (EDC/NHS) chemistry

Dataset on photodegradation of tetracycline antibiotic with zinc stannate nanoflower in aqueous solution – Application of response surface methodology

Removal of pharmaceutical ingredients such as tetracycline from aqueous solution has a great importance. The aim of the current study was to investigate the degradation of tetracycline antibiotic in the presence of a triode semiconductor oxide as well as modeling of the photocatalytic degradation process in order to determine optimal condition Zinc stannate nanoflower (Zn2SnO4) was synthesized by hydrothermal process and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) techniques. Response surface methodology (RSM) was used to model and optimize four key independent variables, including photocatalyst dosage, initial concentration of tetracycline antibiotic (TC) as model pollutant, pH and reaction time of photocatalytic degradation. The proposed quadratic model was in accordance with the experimental results with a correlation coefficient of 98%. The obtained optimal experimental conditions for the photodegradation process were the following: zinc stannate (ZTO) dosage=300 mg L-1, initial concentration of TC= 10 mg L-1, reaction time= 100 min and pH=4.5. Under the optimal conditions, the predicted degradation efficiency was 95.45% determined by the proposed model. In order to evaluate the accuracy of the optimization procedure, the confirmatory experiment was carried out under the optimal conditions and the degradation efficiency of 93.54% was observed, which closely agreed with the predicted value. Keywords: ZTO, Nanoflower, Photodegradation, Water treatment, Antibiotic, Modeling, RS

Covalent Binding of Nanoliposomes to the Surface of Magnetotactic Bacteria for the Synthesis of Self-Propelled Therapeutic Agents

The targeted and effective delivery of therapeutic agents remains an unmet goal in the field of controlled release systems. Magnetococcus marinus MC-1 magnetotactic bacteria (MTB) are investigated as potential therapeutic carriers. By combining directional magnetotaxis–microaerophilic control of these self-propelled agents, a larger amount of therapeutics can be delivered surpassing the diffusion limits of large drug molecules toward hard-to-treat hypoxic regions in solid tumors. The potential benefits of these carriers emphasize the need to develop an adequate method to attach therapeutic cargos, such as drug-loaded nanoliposomes, without substantially affecting the cell’s ability to act as delivery agents. In this study, we report on a strategy for the attachment of liposomes to MTB (MTB–LP) through carbodiimide chemistry. The attachment efficacy, motility, and magnetic response of the MTB–LP were investigated. Results confirm that a substantial number of nanoliposomes (∼70) are efficiently linked with MTB without compromising functionality and motility. Cytotoxicity assays using three different cell types (J774, NIH/3T3, and Colo205) reveal that liposomal attachments to MTB formulation improve the biocompatibility of MTB, whereas attachment does not interfere with liposomal uptake